A system designed to incorporate SMIF permits handling of semiconductor wafers inside and outside of clean room facilities by interfacing a clean semiconductor wafer cassette transport box or pod to a clean environmental housing for semiconductor processing equipment or to other clean environments. The system concept entails mating a box door on a cassette container box to a port door on an equipment enclosure and transferring the cassette into and out of the processing equipment without exposing to outside contamination the semiconductor wafers carried by the cassette.
A standard interface is required for cassette transport boxes intended to control the transport environment of cassettes containing semiconductor wafers. The standard interface addresses the proper transport box orientation for material transfer and maintains continuity between the transport box and semiconductor processing equipment environment to control particulate matter. The SMIF specifications are set out in the Semiconductor Equipment and Materials International (SEMI) standard SEMI E19.4-94 (1992, 1996).
A SMIF system includes minimum volume, sealed boxes used for storing and transporting semiconductor wafer cassettes, canopies placed over cassette ports and wafer processing areas of semiconductor processing equipment so that the environments inside the boxes and canopies in cooperation with clean air sources become miniature clean spaces, and a transfer mechanism for loading and unloading wafer cassettes from a sealed box without external environment contamination of the wafers carried by the wafer cassette.
Wafers are stored and transported in boxes, and wafers are transferred from one of the boxes to semiconductor processing equipment in the following manner. A box is placed at an interface port on the top or bottom of the canopy covering the processing equipment. The box includes a box cover and a box door designed to mate with a port door on an interface port of the processing equipment canopy. Latches release the box and port doors simultaneously, and the box and port doors are opened simultaneously so that particles present on the external door surfaces are trapped between the box and port doors. A mechanical elevator raises or lowers the box and port doors, with the cassette riding on top, into the canopy covered space. A manipulator picks up the cassette and places it on a cassette port of the processing equipment. After processing has been completed, the reverse of the above-described operation takes place.
FIG. 1 is an exploded view of a prior art box or pod 10 and port assembly 12 of semiconductor processing equipment (not shown). Box 10 is a sealable, transportable container and includes a box cover 14 having an interior region 16. Box 10 has a box door 18 positioned at the bottom of box 10 and mounted by port assembly 12 on the horizontal surface of a canopy of a processing station (not shown) of which the semiconductor processing equipment is a part. Port assembly 12 includes a port plate 26, a port door 28, and an elevator assembly (not shown). The elevator assembly transports a cassette holder 30 (FIG. 2) containing semiconductor wafers 32 (FIG. 2) from interior region 16 of box cover 14 into the region beneath the canopy of the processing station.
Box 10 can be alternately pressurized or evacuated when box cover 14 and box door 18 are sealed together to isolate interior region 16 of box cover 14 from ambient conditions. Port plate 26 is connectable to a coaxial injector/extractor 34 at a gas transfer valve 36 (FIG. 2).
FIG. 2 is a cross sectional view of box 10 mated to port assembly 12. Box 10 is designed to sealably mate with port assembly 12; therefore, box cover 14 has first and second box cover sealing surfaces 44 and 46, respectively. Box door 18 has a first box door sealing surface 48 for sealably mating with first box cover sealing surface 44. A gasket 50 positioned and compressed between surfaces 44 and 48 forms a first seal. Port plate 26 has first and second port plate sealing surfaces 60 and 62, respectively. First port plate sealing surface 60 sealably mates with second box cover sealing surface 46. A gasket 52 positioned and compressed between surfaces 46 and 60 forms a second seal. Port door 28 has a port door sealing surface 64 that sealably mates with second port plate sealing surface 62. A gasket 66 positioned and compressed between surfaces 62 and 64 forms a third seal.
Box cover 14 may include a conduit 68 that defines a channel between gas transfer valve 36 and interior region 16 of box cover 14. A filter 70 positioned at one end of the channel filters fluids such as gases passing through conduit 68.
Port door 28 includes an actuating mechanism having two box door latch pins 72 that project from a top surface 74 of port door 28. Pins 72 mate with a box door latch mechanism located in box door 18 to rotate a cam component of the latch mechanism between two operating positions that secure box door 18 to or release box door 18 from box cover 14 to, respectively, close or open box 10. A box door latch mechanism to which pins 72 are matable in a SMIF box is described in U.S. Pat. No. 4,995,430.